What is the meaning of Acts 26:4-5?

4 My manner of life from my youth, which was at the first among mine own nation at Jerusalem, know all the Jews; 5 Which knew me from the beginning, if they would testify, that after the most straitest sect of our religion I lived a Pharisee. (Acts 26:4-5 KJV)

William Burkitt’s Commentary

Here the Apostle Paul begins his defence, with a relation of the innocence and strictness of his life before his conversion: he did and could appeal to all that knew him concerning the unblamableness of his conversion. 

Thence note, That an innocent and blameless life from our youth upwards is a singular support and encouragement to us in a suffering hour especially when we are called forth to suffer for religion and righteousness’ sake.

Observe further, The instance which the apostle gives of his strictness in religion: After the most straitest sect of our religion I lived a Pharisee. Of all the sects among the Jews, none took up such an extraordinarily strict way of religion as the Pharisees; of this sect was St. Paul, before he converted to Christianity, and in this, he rested for salvation.

Thence learn, 1. That an extraordinarily strict way taken up in religion is thought by many a sure and sufficient foundation for their eternal salvation.

Learn, 2. That many may rest upon a strict way of religion, which still comes not up to, but is oft-times besides the appointment of the word of God.

The Pharisees, for their unusual and supererogating way of exactness, concluded that they should certainly go to heaven, if any did; when, alas! many things which they practised with extraordinary zeal and strictness were never required by God at their hands.